Lateral Board Jumps

A boogie or surf board isn't just good for burning calories on the water: It can also be a prop for on-sand workouts, says Chris Freytag, a personal trainer and group fitness instructor in Minneapolis. Stand on one side of your board, facing the same direction the nose is pointed; then hop laterally over the board to the other side. (If you've got a wide board, you may need to stand toward the front where it gets skinnier.) "I call it 'Fire Feet' because you can pretend you're jumping up and over a row of fire," she says. "You can keep your feet together, or you can jump one foot and then the other; the important thing is to keep your knees high." Hop back and forth across the board, 10 times on each side, then rest and repeat for four sets total.

Suicides In The Sand

When Freytag sets up outdoor bootcamps, she uses small traffic cones to mark the "course"—but you can also use anything from your beach bag in their place. "Put your water bottle down in one spot and your sunscreen down a few yards away—or just draw two lines in the sand," she says. Then, for 30 seconds, shuffle back and forth between the two as fast as you can, bending down to touch each marker (or sand line) when you reach it. "Shuffling is really great because it's lateral movement, which most of us don't get a lot of in our normal workouts," Freytag adds. "And being barefoot makes such a difference—it really works muscles that are ignored when we're wearing shoes and on solid ground."

Pull-Ups On A Lifeguard Chair

When lifeguards are off-duty, their chairs can be versatile pieces of fitness equipment: "On most lifeguard chairs, there's a footrest you can do pull-ups or just hang from," says Long Island-based trainer and yoga instructor Jimmy Minardi. (Use your best judgment, and be sure it's stable before putting too much weight on it.) If the chair is tipped over, try doing inclined push-ups or mountain climbers against one of its legs. Or "hang" from a leg with your body in a straight line and feet still in the sand and do modified pull-ups, keeping your body in an upside-down plank position the whole time.

Sit-Ups On Your Towel

When Minardi tells his beach bootcamp clients to spread their towels out on the sand, it's not for a sunbathing break. "Your beach towel is great for all kinds of sit ups and crunches to work your core," he says. To try Minardi's "high-hat" version, lay two towels out end-to-end and grab a partner. Sit facing each other and interlace your feet together (one of you inside and one outside, with feet wrapping around ankles). Keep your knees bent and lower down onto your backs, reaching your arms up overhead. Use your abs to sit all the way up and lean forward, high-fiving each other; the higher the better. Do four sets of 20.

Jumping Jacks And Walking Lunges

Simple warm-up moves on solid ground? Easy. Simple warm-up moves on the beach? Much harder. Jumping jacks get your heart rate up, and because the sand is constantly changing under your feet, it's challenging your muscles to constantly adjust and adapt. "You have to work a lot harder to keep yourself stable," says Minardi, "and that works your core and your entire lower body." Try alternating one minute of jumping jacks—as many as you can without compromising your form—with one minute of walking lunges (another good stabilizing exercise); then repeat for 45 seconds each, then 30 seconds, then 15.

Using Weights Or Bands

You can't carry an entire weight room to the beach with you, but you can certainly fit a pair of 2- or 5-pound hand weights in your bag. Hold onto them while you do jumping jacks or running drills, says Minardi, or use them to do bicep curls and shoulder presses while sitting or lying on your towel. (Adding in a single-leg bridge, as shown, will also work your back, chest, butt, thighs and hamstrings.) For even less weight in your bag, bring along a flat, wide resistance band instead. You can do many of the same basic arm moves, Minardi says, by looping the band around your feet or around a stationery object like a bench or jetty rock.

Fartleks Along The Beach

Running in the sand burns about 30 percent more calories than pounding regular pavement does, and puts many more muscles to work. But to make your outing a bit more interesting—not to mention effective—add some intervals. Fartlek drills are a great option, says Minardi, because you don't need a watch or any set course; you can make it all up on the fly. "Pick a point on the beach—say you see a log in the distance—and sprint to that point," he says. "Then pick another point and jog to that point to recover. Then repeat. Your route can be different every day, and you can always have different markers: landmarks, people, beach umbrellas, you name it."

Planks And Push-Ups On Driftwood

You can do core exercises anywhere, including on the flat sand—but on a slightly elevated surface, like a big piece of driftwood, the moves may feel easier. (Just make sure your prop's not slippery or sharp in any spots!) Try holding a plank for 30 seconds, then do 8 to 12 inclined pushups. Rest for 30 seconds, then repeat, moving your hands slightly farther apart or closer together on the log. Do a total of four sets, experimenting with different positions and working different muscles throughout. Can't find a natural prop? Head up to the boardwalk and find a bench.

Balancing At The Water's Edge

Yoga on the beach can be challenging enough—the sand makes for an uneven and constantly changing surface on which you have to balance. To ramp up the intensity (and the fun), try practicing some postures at the water's edge, says Freytag. Keep your eye on the horizon line as you flow through a sun salutation, holding each pose longer than usual to get the most muscle-toning benefit. High lunges and one-legged postures, like the Warrior sequence and Tree Pose, may be especially challenging as the waves lap at your feet. And because your body has to work extra hard to stay upright, you'll be burning more calories.

Playing Ball (or Frisbee!)

Half an hour of beach volleyball can burn about 245 calories, and can also tone your abs and quads if you keep your core engaged and sneak in some squats while you wait for the ball. Paddleball (also known as Kadima) can burn about 184 calories in 30 minutes, and even playing Frisbee will torch nearly 100. The beach makes it easy to fit in fitness no matter what equipment have with you, says Freytag; you can even dig a hole in the sand or build a sand castle. "Every little bit of activity counts, so anything you do above and beyond sunning yourself on a beach towel is a great way to squeeze in extra burn."